Here are some suggestions for DIS improvements that I cast intot he sea hoping that someone will find time to implement them... 1. Pixel binning. The only advertised choices at present appear to be 1x1 and 2x2. Often one want to bin faint spectra along the slit (esp when the seeing is poor), so 2x1 and 3x1 binning would be very handy. 2. Partial chip readout. I gather time-resolved spectra and need to keep chip readout time to an aboslute minimum. Reading out a patch of the chip would be a great help. Table 1: Guassian fits to a uniformly illuminated slit The trace of a blue lamp line is: pixel 150-160 200-210 250-260 300-310 350-360 400-410 450-460 490-500 center 318.0 318.8 319.4 319.7 319.7 319.5 319.0 318.8 FWHM 1.22 1.30 1.40 1.33 1.30 1.32 1.16 1.25 and for a red line: pixel 90-100 190-200 290-300 390-400 490-500 590-600 690-700 center 338.8 337.5 336.7 336.5 336.8 337.7 339.2 FWHM 1.44 1.57 1.43 2.0 2.2 1.6 1.39 3. Better slit masks. The "standard" 1.5" slit is bent - there is no doubt about it (see table above). It would really simplify life if a new slit with a straight slit were fabricated. We might even consider having a wedge-shaped slit in order to match slit width to seeing conditions for stellar objects. 4. Irregular slit projection. Note the peculiar FWHM's for the slit in the tables above, especially on the red side. This is a result of undersampling (which means that we can't tell if the slit focus is optimized). One onerous result of undersampling (for those of us who observe extended targets) is that we cannot properly subtract sky lines by using portions of those lines that lie near the edges of the chip. Owing to both the apparent slit curvature and the undersampling, night sky subtraction is quite poor for objects more than about 50-100 pixels in size (depending on which part of the projected lsit they are situated). This seriously impairs the utility of the long-slit functionality of the spectrograph. I suppose that the best way to fix the undersampling problem is to use a straight slit that is carefully aligned to rows on the CCD. Another is to use a wider slit (ugh!). Still a third is to use higher magnification in the camera optics (expensive??) --Bruce Balick 9/11/95 APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 5 in the apo35-dis archive. You can find APO the archive in /u/strauss/apo/mailer/apo35-dis on astro.princeton.edu APO To join/leave the list, send mail to apo35-request@astro.princeton.edu APO To post a message, mail it to apo35-dis@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO